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ARM: proc-v7: Ensure correct instruction set after cpu_reset

Message ID 1350384840-28415-1-git-send-email-dave.martin@linaro.org
State Accepted
Headers show

Commit Message

Dave Martin Oct. 16, 2012, 10:54 a.m. UTC 
Because mov pc,<Rn> never switches instruction set when executed in
Thumb code, Thumb-2 kernels will silently execute the target code
after cpu_reset as Thumb code, even if the passed code pointer
denotes ARM (bit 0 clear).

This patch uses bx instead, ensuring the correct instruction set
for the target code.

Thumb code in the kernel is not supported prior to ARMv7, so other
CPUs are not affected.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
---
KernelVersion: 3.7-rc1
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Patch

diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 846d279..42cc833 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -57,7 +57,7 @@  ENTRY(cpu_v7_reset)
  THUMB(	bic	r1, r1, #1 << 30 )		@ SCTLR.TE (Thumb exceptions)
 	mcr	p15, 0, r1, c1, c0, 0		@ disable MMU
 	isb
-	mov	pc, r0
+	bx	r0
 ENDPROC(cpu_v7_reset)
 	.popsection